There were long delays on the M1 Northbound north of Milton Keynes earlier following a five vehicle road traffic collision.
One of the vehicles involved contains hazardous chemicals.
The disruption was between J15 at Northampton and J15A at Northampton Services, with delays of up to two hours on the approach.
Highways England reported that traffic was queuing back towards J14 for Milton Keynes.
The road was closed for a period earlier but all lanes are now open past the scene and traffic has returned to normal.
Northants Fire and Rescue, Highways England and East Midlands Ambulance Service were at the scene.
It follows an unrelated vehicle fire this morning on the M1 Southbound between J15 and J14, which delayed motorists for over 90 minutes.
